A Hybrid ARQ Protocol for the Communication System with Multiple Channels

In this paper, we propose a new hybrid ARQ error control scheme for the data communication system with multiple parallel channels. The receiver is supposed to have some fixed size of buffers (called resequecing buffer) which are used to temporarily store the packets that are correctly received out of sequence. The hybrid ARQ scheme is a combination of Go-Back-N ARQ and Selective-Repeat ARQ protocols. The system operates under the SR-ARQ protocol while there are still some available buffers for the upcoming packets at the receiver. Reversely, the system operates under the Go-Back-N ARQ protocol when the resequencing buffers are totally occupied by the packets which are received out of sequence. We describe the detailed operations of the presented hybrid ARQ scheme and evaluate the system performance (mainly throughput efficiency) under the assumption that the system has two or three different channels. We show the influences of various features on the throughput efficiency and illustrate it at different conditions, such as the number of channels, delay of channels etc. Based on the results of computer simulation, it is clear that throughput efficiency would be reduced by unduly using multiple channels at certain conditions, and introducing buffers at receiver is extremely efficacious as the way to deal with the problem.